Development of Natural Plant Extracts as Sustainable Inhibitors for Efficient Protection of Mild Steel: Experimental and First-Principles Multi-Level Computational Methods

Corrosion inhibition of mild steel by Praecitrullus fistulosus (tinda fruit and peel) extracts

Metal corrosion has recently emerged as a growing concern, impacting both local and industrial operations and disrupting conventional production methods. The utilization of green inhibitors to mitigate the metal degradation has garnered extensive attention from researchers and industrial professionals due to their prominent advantages: high efficiency, cost-effectiveness, and eco-friendliness. A novel ecofriendly inhibitor was prepared from Praecitrullus fistulosus (tinda fruit and peel) for mild steel (MS) corrosion in 1 M HCl. The presence of phenol, 3,5-bis (1,1-dimethyl ethyl)-, 9-octadecenoic acid, methyl ester, hexadecanoic acid 15-methyl-, methyl ester, 9, 12-octadecadienoic acid, methyl ester, 9, 12, 15-octadecatrienoic acid, methyl ester, (Z,Z,Z-), ascorbic acid, and phytol were identified as major constituent through LC/MS analysis of tinda extracts. The existence of these compounds was further confirmed through FTIR analysis, which shows the presence of various functional groups, such as -OH, CO, C-O-C, CC, and aromatic rings in the tinda extracts. Electrochemical and gravimetric analyses were used to investigate the inhibitory effect of tinda extracts. Outcomes of Tafel analysis revealed that both tinda extracts significantly reduced the corrosion current as compared to blank and achieved 83.73 % and 87.59 % inhibition efficiencies at 200 mg L-1 of tinda peel extract (TPE) and tinda fruit extract (TFE), respectively. The change in corrosion potential (Ecorr) was within an ±85 mV range compared to that of the uninhibited system, indicating that both tinda extracts demonstrated a mixed-type inhibition behavior. During adsorption studies, the best fit was obtained for the Langmuir adsorption model. The obtained values of standard Gibbs free energy (ΔG°ads) for TPE and TFE lie between -20 and - 40 kJ mol-1 but close to -20 kJ mol-1, which reveals preferential physical adsorption of the extracts on the metal surface. Thermodynamic parameters, including activation energy, enthalpy, and entropy, were computed across the temperature range of 303 to 323 K, suggesting that corrosion occurs spontaneously by the endothermic process. FESEM analysis depicted that inhibited systems exhibited smooth and crack-free surfaces as compared to blank system. AFM images demonstrated that surface roughness was significantly reduced for the inhibited system. In EDX analysis, the weight percentage of Cl was reduced in the presence of tinda extracts as compared to blank, and in XRD analysis, iron chloride (FeCl2) peak did not appear in the presence of inhibitor but it was in the uninhibited system. All surface-related findings signify that tinda extracts are adsorbed on the MS surface and form a protective layer that separates the metal from the corrosive solution.

Fabrication of Protective Organic Layer Using Schiff-Base Metal Complex Responsible for Excellent Corrosion Performance: Experimental and Theoretical Perspectives

The effectiveness of a copper(II) complex with a Schiff base derived from 2-amino-4-phenyl-5-methylthiazole and salicylaldehyde (APMS) as a corrosion inhibitor for XC18 steel in an HCl solution was investigated. Experimental findings indicated a slight negative correlation between inhibition efficiencies in 1 M HCl and temperature but a positive correlation with both inhibitor concentration and immersion time, respectively. The weight loss measurement revealed that APMS achieved a maximum inhibition rate of 92.07% at 303 K. A fitting analysis demonstrated that APMS adheres to the Langmuir adsorption isotherm. The electrochemical results revealed an enhanced inhibitive performance of APMS, with the efficiency increasing as concentrations increased, ultimately reaching a peak of 94.47% at 5 × 10-3 mol L-1. Potentiodynamic polarization measurements revealed that APMS acted as a mixed-type inhibitor without affecting the corrosion mechanism. Scanning electron microscopy investigations of the metal surfaces corroborated the presence of an adsorbed organic layer. Advanced theoretical calculations utilizing density functional theory and first-principles density-functional tight-binding were conducted to gain insights into the behavior of APMS on the metal surface. APMS derives its advantages from crucial inter- and intramolecular interactions, resulting in the formation of a resilient adsorption layer, in line with the experimental findings. It is found that the presence of the APMS-based inhibitor exhibits a significant synergistic corrosion inhibition effect. The current study offers a design direction for enhancing the structural characteristics of Schiff base metal complexes, laying the groundwork for multifunctional frameworks to minimize corrosion rates with considerations for real-world use and cost-efficiency. The ability to replace harmful, expensive constituents with sustainable, and cost-effective organic alternatives represents a significant outcome of this study.

Corrosion Prevention of Copper in 2.0 M Sulfamic Acid Using Novel Plant Extract: Chemical, Electrochemical, and Theoretical Studies

Copper corrosion was suppressed when a lupine extract was immersed in a 2 M sulfamic acid (H2NSO3H) solution. Numerous methods, including mass loss (ML), dynamic potential polarization (PL), and electrochemical impedance (EIS), were employed in these experiments, in addition to theoretical computations such as density functional theory (DFT), Fukui function, and Monte Carlo simulations. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to analyze the Cu surface's composition and determine its form. Mass loss (ML) was used to examine the inhibition rate of copper corrosion in sulfamic acid at 25 °C in the presence of lupine extract. After examining how it behaved throughout the adsorption process on copper, it was discovered that it follows the Langmuir isotherm and chemical adsorption. An analysis of the PL curves indicates that the lupine extract is a mixed-type inhibitor. It was shown that the inhibitory efficiency increased to 84.2% with increasing lupine concentration. Additionally, as the data show, the efficiency of inhibitors is diminished by increasing temperatures. Theoretical calculations and experimental data were compared using Monte Carlo simulation (MC) and density functional theory (DFT).

Sustainable and Green Corrosion Inhibition of Mild Steel: Insights from Electrochemical and Computational Approaches

Natural and fragrant compounds, essential oils (EOs) extracted from plants through hydrodistillation, are gaining popularity as eco-friendly and sustainable agents to protect metals and alloys from corrosion in acidic environments. This research focused on extracting and characterizing an EO obtained from the Cuminum cyminum (CC) plant native to India. The study aimed to evaluate the inhibitory properties of this EO on mild steel in a 0.5 M HCl solution at different concentrations. Various analytical techniques, including potentiodynamic polarization curves, electrochemical impedance spectroscopy, optical microscopy, infrared spectroscopy, and proton magnetic resonance, were employed to assess the effectiveness of this EO extract. Our findings indicate that the Cuminum cyminum L (CCL) extract effectively reduces the corrosion of mild steel in hydrochloric acid with an inhibition efficiency ranging from 79.69 to 98.76%. The optimal inhibition concentration was 2 g/L of EO, and surface analysis confirmed the formation of a protective layer. Furthermore, our results suggest that the inhibitor binds to the metal surface through a charge-transfer process, creating a protective film. Finally, we utilized theoretical calculations and molecular dynamics simulations to elucidate the inhibition mechanism on both a global and local scale.